Disposal of surface run-off from storm events and the like is a significant problem, particularly in urban areas with a high percentage of paved surfaces. Many older cities in the eastern part of the United States utilize combined storm and sanitary sewers with the combined effluent being treated at wastewater treatment plants. In the event of a large storm exceeding the design capacity of the combined system, direct discharge of raw sewage into receiving waterways may result. Other parts of the country utilize separate storm and sanitary sewers. Localized flooding problems may arise, however, either through under design of the storm water systems or through changes in the run-off patterns resulting from development. Typically such a problem would be addressed by adding additional storm sewers or enlarging existing storm sewers. However, this is a costly process which causes great inconvenience to local residents. In addition, in times of local, state and federal budget deficits, expansion of existing storm water sewers can be difficult to finance.
In areas of rapid growth it is not unusual for a municipality or a developer to need to expand water, sanitary sewers, gas lines, cable access, telephone lines, electrical lines or the like (collectively, “utility lines”) to meet the needs of a growing population. Often these utility lines are financed through specific assessments and management of storm water through expansion of existing storm water sewers is beyond the scope of the construction projects. Construction of these utility lines requires excavation and trenching which, if funding were available, could accommodate expanded storm sewers in a single trenching operation without requiring separate trenching and the attendant destruction and then repair of roadways and sidewalks affected by the trenching.
A conventional prior art utility line trench 10 is illustrated in FIG. 1. The trench 12 is excavated to a depth slightly below the depth a utility line 14 will be placed. A porous particulate material, for example, gravel, forms a bed 16 several inches above the trench bottom 18 and supports the utility line 14. A compactable backfill forms a cover 20 over approximately two-thirds of the utility line 14 outer diameter. The remainder of the trench is filled with native materials 22 from the extraction and the trench is capped with a suitable top soil 24 to promote plant growth. As illustrated in FIG. 1, the conventional utility line trench 10 lies above the mean water table elevation 26, although in instances where the water table elevation is close to the surface, the trench may lie within the water table as well.
One known solution for storage and dissipation of storm water run-off is the use of earth drains. An earth drain is essentially a well connected to an underlying water table which receives surface run-off and rapidly percolates it into the water table. Also known are the use of French drains which consist of a trench filled with a granular porous material such as gravel which can receive and temporarily store surface run-off while the surface run-off percolates to the underlying water table. While such structures provide a means of disposing of surface run-off without having to tap into or expand existing storm water run-off systems, such systems still require trenching and the attendant inconvenience and costs of digging up intercepting roads and sidewalks.
In addition to earth drains and French drains, a number of surface water retention and dissipation structures are known in the art. One example is shown in Glasser, U.S. Pat. No. 4,917,536. Glasser teaches a fluid reservoir consisting of a stack of plastic core sheets bundled together to form a module. While providing a storage structure apart from a storm sewer system, this structure requires additional excavation and is relatively high cost and thus does not provide a solution to the problem discussed above.
Another underground draining system is taught in Urriola, U.S. Pat. No. 5,810,510. The system of Urriola also consists of a storage tank and the storage tank of Urriola is made of perforated wall modules wrapped in a water permeable geotextile. The storage tanks of Urriola provide for temporary storage of water and enable the water to percolate to the surrounding strata. However, like Glasser, Urriola requires excavation to build a large underground tank and requires the use of the costly perforated wall modules and thus does not provide a cost effective solution to the problem discussed above.
Cushing, U.S. Pat. No. 4,620,817, illustrates an example of a French drain structure. Cushing shows a perforated pipe 64 running through a sand and gravel bedding. As precipitation is collected and directed to the pipe 64, water percolates through the perforation 66 and into the sand and gravel bedding and eventually into the underlying water table.
The prior art has failed to provide a utility line bedding or installation method for a utility line bedding that performs the function of supporting the utility line while simultaneously providing water retention and dissipation in a cost effective manner.
The present invention is directed toward overcoming one or more of the problems discussed above.